The tanks should be nearly exactly where the dump valves are. In my coach the freshwater tank sits at floor level with the black and grey tanks on top. My coach is not your coach but it might be a good place to start looking. There should be some removable wall panels allowing VERY limited access but you might be able to find the leaking connection (hopefully) once you get access.
What I post is my 2 cents and nothing more. Please don't read anything into my post that's not there. If you disagree, that's OK.
Can't we all just get along?